1. Field of the Invention
The present invention relates to a method and system for automated control of motor vehicle longitudinal movement.
2. Description of Related Art
Automated control of motor vehicle longitudinal movement typically means accelerating the motor vehicle in an automated fashion in a vehicle longitudinal direction using a drive train of the motor vehicle, for example at an internal combustion engine, or electric motor, and of decelerating it in an automated fashion in the longitudinal direction of the vehicle, using the drive train, or a brake system of the motor vehicle. The acceleration or deceleration being a function of an acceleration variable representing a vehicle setpoint longitudinal acceleration. The term positive acceleration of the vehicle meaning that acceleration takes place in a forward-directed direction of travel. With an acceleration that takes place counter to the forward direction of travel, in the reverse direction of travel, referred to as a negative acceleration or deceleration. Acceleration generally comprises both a positive and a negative acceleration.
Precise longitudinal movement control provides safety and comfort in an autonomously driven vehicle. Currently available commercial comfort systems, for example, adaptive cruise control systems, and under certain circumstances vehicles with a “Stop & Go” function or autonomous parking, are generally assisted by a longitudinal movement controller that accelerates a vehicle within a predefined distance and operates to maintain vehicle speed and stop the vehicle gently.
Controlling longitudinal movement based solely on setpoint value generation of the vehicle longitudinal speed, and during which the vehicle longitudinal speed is reduced to zero as the distance from a predeterminable destination decreases, may not provide a satisfactory result. In terms of a comfortable, essentially jerk-free longitudinal movement of the motor vehicle, the setpoint value generation of the vehicle longitudinal speed, which is based on the distance from the destination, does not adequately take into account the dynamics of the system. Likewise, a longitudinal speed control that is carried out within tight limits on allowable velocity error gives rise to a jerking longitudinal movement of the vehicle, which is perceived as disruptive or at least uncomfortable by the occupants of the vehicle.
Industrial robot controllers use existing methods for jerk limited trajectory planning require considerable computational expenditure, since their algorithms are based on an iterative or recursive calculation. This category includes, for example, the method for jerk-limited trajectory planning which is disclosed in the scientific article “On-Line Planning of Time-Optimal, Jerk-Limited Trajectories” written by Robert Haschke, Erik Weitnauer and Helge Ritter and published at the International Conference on Intelligent Robots and Systems (IROS) 2008.